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How did the Trieste reach the bottom of the Mariana Trench in 1960?

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The Trieste reached the bottom of the Mariana Trench on January 23, 1960, using a specialized bathyscaphe design developed by Auguste and Jacques Piccard.12

To achieve this, the vessel utilized two primary components: a pressure-resistant steel cabin for the crew and a large float filled with gasoline. Because gasoline is lighter than water, it provided the necessary buoyancy to lift the heavy cabin.2

The descent and ascent were managed through controlled buoyancy:
* Descent: On the surface, air-filled ballast tanks provided lift. By opening valves, the air was replaced by water, increasing the vessel's weight to initiate the dive. As the vessel descended, the gasoline was compressed by the increasing sea pressure, causing a gradual loss of buoyancy that accelerated the descent.2
* Ascent: To slow the descent or begin returning to the surface, the pilots released iron shot ballast stored in silos, which was held in place by electromagnets.2

This technology allowed Jacques Piccard and U.S. naval officer Don Walsh to reach a record depth of 35,814 feet (10,916 metres) in the Challenger Deep.12